During sampling and/or drilling operations, sonic or acoustic measurements may be obtained using a downhole tool to determine formation parameters, for example. These formation parameters may be used to obtain a better understanding of the formation.
When making acoustic measurements to determine formation parameters in a logging-while-drilling (LWD) environment, the acoustic properties of the drilling fluid in the annulus surrounding the drill string may be quantified to enable a more accurate determination of the formation properties. In other words, the affect of the drilling fluid on the manner in which acoustic signals propagate away from and toward an acoustic LWD device may be accounted for when calculating or otherwise determining the formation properties or parameters from such propagated signals. It is relatively simple to measure directly the properties of drilling fluid within a tool string or drill collar. However, due to the presence of rock cuttings, the properties of the drilling fluid in the annulus are different than those of the drilling fluid within the tool string or drill collar and directly measuring the properties of the drilling fluid in the annulus is very difficult.